1. Field of the Invention
The present invention generally relates to an organic light emitting diode device, and more particularly to an organic light emitting diode device of which a color temperature is adjustable.
2. Description of Prior Art
An organic light emitting diode (OLED) device can be used as a light source for display devices and illuminating devices. The organic light emitting diode device mainly comprises a substrate, an anode disposed on the substrate, a light emitting layer disposed on the anode, and a cathode disposed on the light emitting layer.
When a potential is applied between the anode and the cathode, holes are injected from the anode to the light emitting layer and electros are injected from the cathode to the light emitting layer. The holes and the electrons recombine in the light emitting layer. The recombination of the electron holes and the electrons will release energy which will excite carriers in the light emitting layer to emit light, and thus the light emitting diode device is also called an electroluminescent (EL) device.
A color temperature refers to a color change which human eyes senses when the energy level of the light is different. In the organic light emitting diode device, the color temperature is controlled by a carrier concentration of the light emitting layer. When the carrier concentration of the light emitting layer is fixed, the color temperature which the organic light emitting diode device can show cannot be adjusted any more. Accordingly, applications of the organic light emitting diode device are limited.
Thus, there is a need to solve the above-mentioned problem that the color temperature is not adjustable.